Problem: Daniel is 3 times as old as Tiffany and is also 4 years older than Tiffany. How old is Tiffany?
Answer: We can use the given information to write down two equations that describe the ages of Daniel and Tiffany. Let Daniel's current age be $d$ and Tiffany's current age be $t$ $d = 3t$ $d = t + 4$ Now we have two independent equations, and we can solve for our two unknowns. Since we are looking for $t$ , and both of our equations have $d$ alone on one side, this is a convenient time to use elimination. Subtracting the second equation from the first equation, we get: $0 =$ $3t$ $-$ $ (t + 4)$ which combines the information about $t$ from both of our original equations. Solving for $t$ , we get: $2 t = 4$ $t = 2$.